Hi,

Basically in the case of 1 instance, we can't really use the refresh instance mechanism if we want zero downtime. What I found people doing is what Shahad suggested. I.e. : determine that you are running only 1 instance -> increase the desired capacity --> decrease it back. The problem that I'm having with this solution is the timing. In my case, It's a lambda that triggers the Instance refresh after a new AMI is available. So, in the case of 1 running instance, that lambda could indeed increase the desired capacity to 2, but does not it have to wait until that instance is fully available before it resets the desired capacity back to 1 on the ASG otherwise we are back to the dreaded down time....? I could force the lambda to wait for that time with a loop checking on the status, but that's everything but elegant not to mention the billing time that, that incurs... Any ideas? Any event we could listen for....

I have read about the 'create_before_destroy' terraform solution which basically duplicate the whole ASG to ensure high availability. What do you guys think about it?